This application is based upon and claims benefit of priority of Japanese Patent Application No. 2001-305601 filed on Oct. 1, 2001, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electronic impact sensor for an air-bag system protecting passengers from a collision impact of an automotive vehicle.
2. Description of Related Art
An air-bag system for protecting passengers from a collision impact has been used in recent automotive vehicles. An example of a conventional sensor 50 for electronically detecting a collision impact for use in the air-bag system is shown in FIGS. 3A and 3B. The impact sensor is installed in a collision impact receiving space such as an engine compartment.
An impact sensor circuit board 52 is mounted on a resin case 51, and a connector 53 for sending sensor signals to an electronic control unit (not shown) for an air-bag system is connected to a rear side of the resin case 51. When a vehicle collision occurs, an impact sensor on the circuit board 52 detects a collision impact and sends electrical signals to an electronic control unit for controlling operation of an air-bag. The air-bag is inflated for protecting passengers when the detected collision impact exceeds a predetermined level.
In order to obtain the sensor signals without fail in such a collision, the impact sensor 50 itself has to be protected from vehicle structures damaged by the collision. For this purpose, an entire sensor 50 including the circuit board 52 and the connector 53 is encapsulated in a metallic case 54. The encapsulated sensor 50 is connected to a bracket 55. The bracket 55 is mounted on a support frame (not shown) in an engine compartment by screws 56. However, since the entire sensor 50 has to be encapsulated by the metallic case in the conventional structure, a cost for manufacturing the sensor becomes expensive.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved electronic impact sensor which is protected from the structures damaged by a collision without using a costly metallic case encapsulating the sensor therein.
A circuit board having an impact sensor element thereon is mounted on a supporting member composed of a mounting base and a protecting member integrally formed with a resin material. The mounting base includes a depressed portion and a pair of thick portions formed at both sides of the depressed portion. Tapered front walls forwardly descending from the depressed portion and the thick portions are formed at the front side thereof. The circuit board is mounted on the depressed portion, so that the circuit board is protected from vehicle structures damaged by a collision impact.
The protecting member having a pair of parallel protecting walls is integrally connected to a rear side of the mounting base. A pair of tapered sidewalls are provided for firmly connecting the protecting member to the mounting base. A connector for leading out electric signals from the circuit board is disposed in the space between the pair of protecting walls, so that the connector is protected by the protecting walls when a vehicle collision occurs.
The supporting member is fixed to a support frame by pair of screws inserted through the thick portions. Each screw is surrounded by a collar tube to enhance its mechanical strength.
Since the circuit board and the connector are disposed in spaces protected by solid structures of the supporting member, they are prevented from being hit by vehicle structures falling apart when a collision occurs without covering them with a metallic case which is conventionally used. Accordingly, the electronic impact sensor can be made compact and manufactured at a low cost.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings.